Telephone system



March 24, 1931.

B. WALLACE 1,797,935

TELEPHONE SYSTEM 2 Sheets-Sheet 1 Filed Jun 17, 1929 JUL/5172017 March 24, 1931. B, WA LA E 1,797,935

TELEPHONE SYSTEM Filed June 17, 1929 22/572727"? .5577 Z/Z/EZ/EEE Patented Mare 24, I931 q. :2: Lemma.

BERT WALLACE,

5N1?" OFFICE- QF CHICAGO, ILLINGIS, ASSIGNOR T0 KELLOGG'SWI'ICHBOARDAND SUPPLY COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS TELEPHONE SYSTEM Application filed zruneiiv, 1929. Serial No. 371,393.

' My inventionrelates to telephone systems and has to do more particularly with cord,

circuits of branch exchange systems such as areus'ed for interconnecting local ortoll sub scribers linesterminating at a branch exchange switchboardand for also connecting the local or toll subscribers lines terminating at the branch exchange with subscribers lines terminating at a main exchange.

An object of my invention is the provision of 'an'improved circuit arrangement which has desirable features of operation in interconnecting subscribers lines as calling and called. lines, all in a simple, eificient and economical manner. 7

In a branch exchange system it is desirable in addition to the usualtoll to toll connec tions, to connect a toll subscribers line terminating at a branch exchange switchboard with a subscribers line terminating at a main exchange and a' feature'of my invention is the provision of a universal toll cord circuit I ings, at the left of part 1, I show a calling which is adapted to interconnect toll or local substations as calling and called lines or toll or local substations with subscribers lines terminating at a main exchange.

Another feature of my invention is the arrangement of the universal cord circuit of my invention whereby both cord plugs of a cord pair have associated therewith apparatus to permit either plug of the cord pair to be connected with a calling line or to extend a connection by way of a trunk connection to a called line terminating at a main exchange system.

Another feature of my invention is the provision of a calling or impulsesending device which, through the medium of a pair of come mon dialing keys, maybe connected to either plug of acord pair to permit dialing on either end of a cord pair to establish a connection with a subscribers line-terminating at a main automatic exchange. p

Another feature of my invention 1s the'provision of means in the cord'circuit whereby an operator, attempting to answer a'second call before completing a preceding connection is prevented from being connected with the second calling line until the other connection is completed.

Still another feature of my inventionis the provision of a key, common to an operators position, which may be actuated when the V listening key of a cord is in its talking position, toconnect the operators set with either the calling or the called end ofanestablished connection to permit the -"operator to converse with either'of the substationsconnected to the respective ends of the cord.

The above features, as well as others not partlcularly'pointed out and through the provision of which the above mentioned and other advantageous results are attained, will bedescribed by reference to the accompanying drawing in which Part 1 and part 2 taken together with the lines terminating at the right in part I joined to the respectlve lines terminating at the left in part 2, form a circuit diagram .of the universal toll cord circuit of the present invention. I

Referring now to the accompanying drawtoll or magneto substation A terminating at the branch or toll switchboard in a line circuit L comprising a drop signal DS, a cutoff relay CO andmultiple jacks J. 'Thecord O illustrated in partsl and2 is provided with connecting plugs P and P which may be interchangeably used as answering and calling plugs. A listening key LK is provided which, when actuated in response to a call, controls the operation of a listening control relay GR, which relay in turn controls the operation of the operators listening relay OR. The actuation of the listening key LK also controls the operation of the operators connecting relay OP associated with the operators circuit 00 shown in part 2. The operators set is connected to the cord O through the medium of relays OR and OP. Sleeve relay SLand an auxiliary sleeve relay SL, associated with. the plug P, are aifecteddifferentlydepending upon the type of line to which the plug P is connected. Sleeve relayxSL and an auxiliary sleeve relay SL are associated with plug P" and are also affected differently depending upon theitype of line to which the plug P is connected' An auxiliary listening key AL of the double cut ofi type, common to a position having a plurality of cord circuits such as the one here shown, may be actuated in association with an actuated listening key of a connected cord to permit the operator to converse with either the calling or called line of an established connection.

A repeating coil connecting relay RS, the energization of which is under the control of either relay 'SL or Slffcontrols. the connection otthe repeating -coil BC with the tip and ring conductors of the cord C. This connection of the repeating coil BC in circuit with the tip and ring conductors depends upon the type of line to which the plug P or'P of the cord Cis connected. A polarized relay PLgwhichserves as a supervisory relay, receives, current from the calling or called substation in a tell to toll connection, when either substationgives the disconnect signal upon the termin tion of conversation, to bring about the lightn of the supervisory signal AS. The di tr control relays DC and DC" are associated respectively with the plugs .P and P and through the medium or" thedialing keys DK and DK,' the calling device D, which is cominoirto the posi tion may be connected with either of. the plugs P or P when the same are connected to a trunk extending to a,niain automatic exchange. The polarized relays PL and PL are associated respectively with the plugs P and P and control the lighting of thesupervisory signals AS and. ,CS' when either plug P or P is connected with a trunk extending to a main automatic exchange. The ringing keys. RK and RK, associated respectively with the plugs P andPQare for the usual purposes. To the right in part. 2 I show a called toll or magneto substation B terminating at the branch exchange in a line circuit L comprising a drop signal DS, a cutoff relay CO and a multiple jack J".. I also show a trunk circuit T which terminates at .its one end at the branch exchange switchboard in a trunk jack TJ and its other end in an automatic exchange and to which either plug P or P may be connected. A relay CO associated with the trunk jack TJ; con trols the lighting of the busysignal lamps BL.

Having described in general the apparatus comprising the universal toll cord circuit C of my invention I will now describe in detail the operation of the same.

Assuming now that the subscriber at the toll or magneto substation 1n1t1ates a call, current from the actuated hand generator HG at the substation A causes the operation of the drop signal DS. The circuit being traced through normally closedcontacts 2 and 3 of the cut-off relay GO of the line circuit L which terminates at the branch exchange. The operator associated with the toll cord circuit C noting the actuated drop signal DS, inserts the plug P of the toll cord sleeve contacts of the connected plug P and jack J to ground through the cut-oil relay C0 of the line circuit L. The cut-cit relay CO and the auxiliary sleeve relay SL are energized over this circuit but, due to the high resistance of the cut-off relayCO the sleeve relay SL remains unenergized. Upon the energization of the cut -oft relay CO its normal contacts 2'and 3 are opened to disconnect the drop signal DS from the line conductors and the secondary sleeve relay SL energizes and closes its alternate contact 6 for purposes which will presently be described. v l i The operator now .actuates thelistening key LK, closing alternate contact 7 to establish an energizing circuit for the listening control relay CR traced from battery through low and high resistance windings 8 and 9 of the relay CR, conductor 10, alternate contact 7 of the listening key LK, to ground through the resistance 11. uponenergizing closes its alternate contacts 1-2, l3, 14, 15 and 16. The closing or" alternate contact 13 establishes a substitute circuit through the relay CR traced from battery, through, the low resistance winding 8, alternate contact 13, and alternate contact 7-, to ground through the resistance .11. The closing of alternate contact 12 of the relay CR establishes an energizing circuit for the operators listening relayOR traced from battery, through the winding of relay OR, conductor 17 to ground through alternate contact 12 of the relay CR. Relay OP closes its alternate contacts 18, 1:9, 20, 21 and 22. The energization of relays CR and OR is for purposes which will presently be described.

The closing of alternate contact 23 of the listening key LK establishes an energizing circuit for the operators connect-ing relay OP, associated with the operators circuit 0C, traced from battery, through the winding of the relay OP, conductor 23 to ground atelternate contact 23 of the listening key LK.

Relay OP operates to close its alternate contacs 24c, 25, .26, 27 and 28. The closing of alternate contacts 25 and 28 of the relay OP connects the operator s receiver 29 to the tip and ring conductors of .the cord 0 over a circuit through alternate contact 28 of relay OP conductors 29 and 30, normal contact 31 of the auxiliary listening key AL, which is common to an operators position, conductor 32 The relay CR,

and through alternate contact21of the relay 1 3 OR to the ring conductor of the cord 0. j The connection to the tip conductor of the cord C is traced through alternate contact 25 of the relay OP, the winding 33 of the induction coil IO, conductor 34, normal contact 35 oi the key AL, conductor 36 and through alternate contact. 19 of the relay OR to the tip conductor of the cord C. The operators transmitter 3? is connected inductively to the tip and ring conductors of the cord C over conductors 30 and 34 and the path just de scribed, through the windings of the induc tion coil 1C. The operator having been connected to the cord C as just described now in-, quires the Wants of the calling subscriber at the substation A, and, assuming the sub scriber at the toll or magneto substation B is Wanted, 'she tests the jack of the wanted line as to its idle or busy condition by placing the tip conductor of the plug P sleeve conductor of the jackJ; c

It the wanted line is busy the sleeve of the jack of the wanted line'will be at battery potential and this battery potential will eX tend from the tip of the plug P of the cord C through normal contact 38 of the dialing control relay DC, normal contact 42 of the relay SL conductors 43 and, 44, alternate contact 14 of relay CR, conductor. 45 to,

ground through the Winding of the test relay TR of the operators circuit 00, Therelay energizes over this circuit and the opening of its normal contact 46 will remove the; shunt from the winding 47 of the induction coil ICto give the operator the usual busy indication.

It the operator upon testing it, finds the wanted line idle-she inserts the plug P into the jack J of the called line and actuates the ringing key RKto impress rin ing current from the ringing generator (5? on the 7 called line. The insertion of the plug P into a the aok J establishes a circuit traced from battery through the winding of the relay SL conductor 48, Winding of auxiliary sleeve re-i lay SL conductor 49, the sleeve contacts of the connected plug P and jack J to ground through the Winding of the cut-01f relay C0 of the line circuit L. The cut-off relay CO energizes over this circuit to open its normally closed contacts 2 and 3 to remove the drop signal DS from the control of thecalled subscriber. The sleeve contacts of the multiple jacks of the line are thus joined to battery so the line willtest busy. The auxiliary sleeve relay SL is also energized over this circuit to close its alternate contact 42 but the sleeve relay SL does not energize due to the high resistance of the cut 05 relay C0.

The operator, having tested the line and actuated the ringing key Bl; to signal called substation B, now restores her listening key LK. The opening or" alternatecontact 'Z' of the restored listening hey opens the energiz ing circuit ofthe relay which now r against the the sleeve relays SL and SL do not stores and by opening its alternate contact 12 4 interrupts the energizing circuit of the relay.

OR which restoresto normal and again closes its normal contacts 19 and 21 to again close the continuity of the tip and ring cord conductorsn The called subscriber at the substation 13, in response to the call signal at thesul station, removes. his receiver from the switchhook and this act stations andB in conversational circuit.

This talking circuit may be traced over the of the sleeve relays SL and SL and the normal contacts 63, 5?, 19 and 38 of the respective relays DC, RS, GR and DC in the tip condoctor and normally closed contacts 61 anc.

21 of the relays RS and OR in the ring conductor. 'F or reasons previously described, energize when the respective plugs P and P are inserted in the jacks J and J of the calling and: called magneto lines A and B. As the energization of the repeating coil switching relay RS controlled by'either relay SL orSL no energizing circuit is establishedcfor same, and in the connection just described, the repeating coil RC is not included in the tal ing circuit.

The operator may-supervise the connection by actuating the monitoring key MK to close the alternate contacts 50 and 51 to connect the operators receiver circuit across the tip and ring conductors of the cord C, the connection extending over conductors 52 and 53, through alternatecontacts 50 and 51 of the monitoring key MK, conductors 54 and 55"to normal contacts 24 and 2.7 of the relay OP of the operators circuit C and through the repeating coil RC associated with the operators circuit 0C. The operators receiver 29 is inductive lyassociated wlth the coil-RC in a manner wellunderstood.

Should the operator associated with the cord C attempt to answer another call before she has completed the connection now being described, the actuation of a listening key LK of another cord at this operators position will connect the high resistance ll, which is common to the operators postition, through the alternate contact? of the actuated listening key in thesecond cord in circuit with the relay GB of the second cord. This second relay CR- will not operate, however, due to the shunting effect of the low resistance wind the places the calling and called subscribers the respective subheavily marked tip and ring conductors WhlClllIlClUdG the alternate contacts 6 and 42 n normally closed cont V SS, traced from battery 7 tact 70 of the key All,

, ring conductors of cord c'alling or caller, subscriber before the conversational circuit is established between the spective substaticr" To th 'enrl I provide an auxiliary listei ke 1 cut-0E type which is com on to theopen tors position. Assuming that the operator wishes to converse with the ca l subscriber substation l3 before connecting the subscribers in conversational circu the auxiliary listening key AL is a tuatec 0 open the "s 31 ar )=J'(.J.1( l. close the normally open co ct TC- associated with the left hand of contact sp The listening key LK, asso ated wi is also a tuated to ng alzout oi": the relays and ct th relay of the over previously descrired. The cl normally open 70 of the is of contact springs est circuit for the superv LA a 1 abllsnes an eneigizin "cry witc ing relay h ewinding of relay SS, alterna; t 29 or relay (Eli and conduct-o1 ground 21:? alternate con- T ition represently lay SS is for p be described, OP, the operator conductors 30 and M tacts 71 and 72 of Kit Lane s L springs of the key AL, over conductors 7? a -1. 78, through alternate contacts 22 and 18 oil the relay OR, to the ring tip conductors of the callin end of the c {l G.

C are open at the contacts 19 and 21 or" the relay thus disconnecting the operator from the answering end of the cord C. The opera r may now converse with the called subs *iber at sul station B.

To converse with the calling subscriber at substation A to the exclusion of the subscriber at substation B the operator actuates the key AL to open the normally closed contacts 71 and 72 and close the normally open contact 78 of the right hand set of springs of the key AL. The operators set is new con- 7 the deenergization of relays SS, OR and CR of'thecord C and the deenergization of the relay OP of the operators circuit 06. The

restoration of relay OR 01" the cord C permits contacts 19 and 21 to close the continuity of the tip and ring conductors of the cord C.

o will now'assume that the conversation betweenthe subscribers at substations A and of the double The tip and B has terminated and the subscribers replace their receivers upon their respective switchhooks. The actuation of the hand generator the calling substation A will send an impulse of current from the generator through the tip contacts of the connected ja'ck J and plug P, the normal cont-act 79 of the ringing key BK, normal contact 63 of the relay DC, alternate Contact 6 of relay SL, the winding 0; of the repeating coil HG, conductor 86, normal contact 82 olrelay for the rela 92, traced from battery through the winding of relay 92, togroi'i'nd at alternate centactf91 of the polarized relay PR. The relay is energized and closes a locking circuit for itself traced from battery through its =winding, its alternate contact 93, conductor 94, to ground at'nor'rnal contact 23 of the listening key LK. The closingot alternate contact 98 of relay 92 also closes a circuit for the supervisory signal AS, traced from battery through the lamp AS, normal contact 83 of relay SL, conductor 95, normal contact 60 of relay RS,'conduct-or 96, alternate contact 93 of relay 92, and conductor 94: to ground at normal contact 23 of the listening key LK. The supervisory signal AS is lighted over this circuit and indicates to the operator that the conversation has terminated. Should the called subscriber at the substation B be the one to operate his hand generator to give the disconnect signal, current from the hand generator HG at the called substation B will operate the polarized relay PL over the tip conductor of the cord C, through the winding Mot the repeating coil BC, the windings ot' the relay PL, the winding 6 of the repeating coil BC to the ring conductor of the cord C and back to the hand generator HG. The relay PL now operates as before described to operate the relay 92 which in turn closes a circuitfor the supervisory signal AS. The operator noting the lighted lamp signal AS, now Withdraws the plugs P and P from their respective jacks J and J and also actuates her listening key LK. The key 'LK, when actuated, opens its normal contact 23, which interrupts the locking circuit of relay 92, which restores to normal, and also opens the energizing circuit of the supervisory? signal AS. The removal of the plugs P and P from the respectivejacks J and J permits the sleeve relays SL and SL of the cord C and the cut-off relays CO and CO restore and the apparatus used in establishing a connection betweenthe substations A and B is now at 'normaland establishing other connections.

Referring again to the, operation of the auxiliary listening key AL, the actuationof this key brings about the. operationofthe supervision switching relaySS as previously described. Should the'called subscriber at subs'tationB operatethehand generator HG to give the'disconnectsignal while the operator of the cordG is conversing with the calling subscriberat'fthe substation A, the current from the hand generator HG extends over the tip conductor of the cord C, through alternate contact 74 of the relay SS, conductor 98, normal contact'99 of the relay SL conductors 103 and 88, the windings of the polarized relay PL, conductor 89, normal,

contact 102 of relay SL conductor 104, alternate contact- .75 or" the relay SS to the ring conductor of the cord Cand back to the hand generator HG at the substation B. The relay PL is operated by current over this circuit and closes a circuit for the relay 92 as previously described. The relayf92 is locked up over a circuit to ground at alternate contact 105 otthe relay SS, insteadof the locking-ground at normal contact .23, of the listening key LK, as in this instance the listening key LK is also actuated to open its normal contact 23 wh'enthe auxiliary listening key AL is actuated. The circuit of the supervisory signal AS is alsoclosed to ground through alternate contact 105 of the relay SS. The lighted signal AS indicates to the operator that the called subscriber at sub.- station B has given a disconnect signal. The operator now removesthe plugs P and P from the respective jacks J and Jand restores the keys AL and LK and the apparatususedin establishing the connection is restored as previously described.'

Assuming now that the toll subscriber at the magneto substation A initiates a call and wishes to converse with a subscriber whose line terminates at an automatic exchange, the operation of the circuit is the same as previously described up to and including the inquiry of the operator in response to the actuated drop signal DS. The operator, upon receiving the number of the main or change subscriber, inserts the plug P into an idle trunk ackTJ, establishing an energiz ing circuit for the cut-off relay CO associated with the trunk jack TJ and the-sleeve relays SL and SL of the cord 0, traced from battery through the winding of the sleeve relay SL conductor 48, Winding of the sleeve relay SL conductor 49,the sleeve contacts of the connected'plug P. and trunk jack TJ to ground through the winding of the trunk cutoff relay C0 The sleeve relays Sl'fiand SL and cut-off relay CO enavailable for ergize over thiscircuit, the sleeve relay SL closing its alternate contact 42 and thesleev e relay SL closing its alternate contacts 99, 100, v101 and 102. The cut-ofi relay CO energizes to close its alternate contact, 110 to light the busy lamps BL associated with the Inultipletrunk jacks TJ which indicates the busy condition ofthe trunk with which the plug P is associated. Theclosing of alternate contact 1000f the relay SL 'estabblishes an energizing circuit for the repeating coil switching relay RS, tracedfrom battery, throughthe winding otrelayRS, conductors' 1.11 and 112 to ground at alternate contact 100 of relay SL The relay BS energizes and closes its alternate contacts 57, 58, 59, 60 and 61 which connect the windings a, b, Wand d of the repeatingcoil across the tip and ring conductors ofthe cord (1. The closing of alternate contacts 99 and 102 of therelay SL closes an energizing circuit for the polarized relay PL which receives battery current over a circuit traced from battery through the Winding of theimpulse relay IR at the main exchange, the tip contacts of the connected trunk jack TJ and plug P, normal contact of the ringing key RK, norinal'contact 38 of the relay DC, alternate contact 42 0f relay SL normal contact 19 of the relay OR, alternate contact 57 of relay RS, the winding 0 of the repeating coilRC, conductor 114, normal contact 74 of relay SS, conductor 98, alternate contact 99 of relay SL conductor 115, through the windings of the polarized relay PL conductor 116, alternate contact 102 of therelay SL conductor 104, normal contact'75 oi the relay SS, conductor 117, the winding (P7 of the repeating coil RC, alternate contact 61 of the relay RS, normal contact 21 of the relay OR, normal contact of the ringing key BK, the ring contacts of the connected plug P and jack TJ to ground through the winding of the impulse .relayIR at the automatic main exchange. The polarized relay FL is energized over this circuit and its alternate contact 120 establishes a circuit for the calling supervisory lamp CS, traced from battery through the lamp CS, alternate contact 101 of relay SL conductors 118 and 119 to ground at alternate contact 120 of relay PL The relays CR and OR are energized due tothe actuation ofthe listening key LK as before, the relay CR operating to preventthe operator from connecting to a second cord, in the manner previously described.

The operator, having inserted the plug P in the trunk jack TJ to cause the operation of certain instrumentalities of the cord C as above described, now actuates the dialing key DK which is associated with the plug P and common to an operators position. This closes an energizing circuit for the dialing controlrelay DC, traced from battery through'the winding of the relay DC, conalternate contact 120 of the relay PL? ductor 121,. alternate contact 15 of the relay CR, conductor 122, to ground at. alternate contact. 123 of the dialing key. DK". The

closure of alternate contacts 39 and a of the relay DC established a locking circuit for itself, traced from battery through the winding of relay DC, the alternate contacts 39 and 40, conductors 118- and 119 to ground 1at Tie closing of alternate contact of the relay DC also closes a circuit for the dial pilot lamp DP, traced from battery through the lamp DP, conductor 1241, alternate contact of relay DC, conductors 118 and 119,v to ground at alternate contact 120 of the relay PL for purposes which will presently be described. The closing ofi alternate contacts 37, 38 and 41 of the relay DC bridges the impulse dial D, associated with the cord C and common to the operators position, across the tip. and ring conductors of the cord C and in circuit with the impulse rela r IR at the main automatic exchange The impulse circuit may be traced from battery through the winding of the relay IR at the main exchange, tip contacts of the connected plug P and jack T J normal contact of the ringing key BK, alternate contact 38 of relay DC,- conductor 128, closed impulse spring contacts, 129 and 125 of the dial D, normal contact 126 of the dialing release key DI, conductor 127, alternate contact 37 of the relay DC, alternate contact 12 of relay SL alternate contact 18 of relay OR, conductor 78., normal cont-acts 72 and35 of the auxiliary double cut-oft listening key AL, conductor 36, alternate contact 19 of relay OR, alter natc contact 57 of the, relay RS, the winding 0 of the repeating coil RC, conductor'llt, normal contact 74: of relay SS, conductor 98, alternate contact 99 of relay SL ,conduc.- tor 115, the windings of the polarized relay PL", conductor 116, alternate contact 102,, conductor 104, normal contact of re lay SS, conductor 117, the winding d of the repeating coil RC, alternate contact 61 of relay RS, alternate contact 21 of relay OR, conductor 32, normal contacts. 31 and 71 of the key AL, conductor 7 7 alternate contact 22 of relay OR, normal contact of the ring key BK, ring contacts of the plug P and trunk jack TJ to ground through the other winding of the impulse relay IR at the main automatic exchange. The opening of normal contact 38 of the relay DC opens the initial energizing and bridged across the tip and ring conductors of the cord C over the circuit just described.

The operator now actuates the calling or impulse device D to send a series of impulses corresponding to the digits of the number of the wanted subscriber. Each time the impulse device is moved from normal the shunt spring 130 is moved into engagement with the impulse spring 125 to. bridge the resistance-13l across the tip and ring conductorsof the cord through alternate contacts 38 and 41 of the relay DC and upon the subsequent opening and closing of the impulse springs 125 and 129, each impulse will extend through the resistance 131 and the alternate contact 38 and 410i the relay DC instead of the bridged circuit, previously described. After the last digit of the number of the called subscriber has been dialed and, assuming that the line is idle, certain instrumentalities in the circuit at the automatic exchange operate in a manner well understood, to reverse the flow of battery through the windings of the polarized relay PL over the circuit above described causing its armature to open its alternate contact 120 and efface the supervisory signal CS and dialing pilot signal DP. The efiacement of the two signals gives the operator of the cord C an indication that the call has been extended to. the called line. The opening of alternate contact 120 of the polarized relay PL also opens the locking circuit of the relay DC which restores to normal to disassociate the impulse dial D fromthe cord C. The'operator now actuates the ringing key RK' to connect the generator G to the line to signal the called subscriber at the main exchange. As-the listening key LK is in its. off normal position the operator may supervise the connection. When the called subscriber answers, in response to his call signal, the operator restores the listening key LK. The opening of alternate contact 7 of the keyLK opens the energizing circuit of the relay CR which now restores and in turn opens the energizing circuit of the relay OR. The calling subscriber at the; magneto substation A and the called subscriber at the main automatic exchange are now in a conversational circuit which may be traced over the heavily marked conductors which, in a. trunk connection such as just described, include the windings a and b, and 0 and d of the repeating coil RC,'connected in the talking circuit through alternate contacts 57, 58, 59 and 61 of the relay BS.

The subscribers at the respective substations in the connection just described, having finished their conversation,replace. their re ceivers upon their respective switchhooks. The subscriber at the calling toll or magneto substation A, after replacing his receiver upon the switchhook, actuates the hand generator HG to send an impulse of current through the windings of the polarized relay PL over a circuit previously described. The relay PL closes a circuit for the relay 92 which is locked up to ground at normal contact 23 of the listening key LK. The closing of alternate contact 93 of the relay 92 closes a circuit for the answering supervisory signal AS, traced from battery, through the supervisory signal AS, normal contacts 83 and seer relay SL, conductor MO, alternate contact 60 of the relay RS, conductor 96 to ground at normal contact 23 of the listen key Lit: over the path previously traced in connection with relay 92; The lighted signal AS gives-the opeiatorv of the cord a disconnect signal as previously de scribed. The called subscriber, at the main automatic exchange, replacing the receiver at the substation, operates instrumentalities at the main, exchange which again reversethe flow of battery through the windings of-the polarized relay PL to cause the same to again close its alternate contact 120 to light the calling supervisory signal CS. The operator of the cord 0, noting the lighted supervisory signals AS and CS, now removes the plugs P and Pfrom the respective jacks J and TJ. The removal of the plug P from the jack J opens the series energizing circuit of the cut-off relay C0 of the line circuit L and the sleeve relay SL of the cord C and the said relaysrestore. "The operator now momentarily actuates the listening key LK to open its alternate contact 23 thus interrupting the locking circuit of the relay 92 which restores and interrupts the circuit of the answering supervisory signal AS. The removal of the plug P of the cord C from the trunk jack TJ opens the series energizing circuit for the cutofi relay CO associated with the trunk jack TJ and the sleeve relays SL and SL of the cord C. The opening of alternate contact 101 of the relay SL efiaces the calling supervisory signal CS and the opening of alternate contact 100 opens the circuit of the repeating coil switching relay RS which restores to disconnect the repeating coil from the tip and ring conductors of the cord C. The relay CO restoring, opens its alternate contact 110 to efiace the busy lalmp'signal BL. The apparatus used in establishing the connection just described is nowat normal and available for establishing other-connections.

Referring again to the dialing operation by the operator associated with the cord C in subscriber at substation A to a subscriber terminating at the automatic main exchange, should the operator inadvertently dial the Wrong number, she may release the connection by actuating the dial release key DI. When the normal contact 126 of the dialing release key DI is opened it interrupts the dialing'circuit to effect the release of the automatic switches at the main exchange. The opening of normal contact 126 also opens the energizing circuit of the polarized relay PL which circuit extends through the normal contacts of the'impulse springs of the calling device D, over a circuit previously described. The relay PL in restoring, opens its alternate contact 120 to interrupt the locking circuit of the dialing control relay DC ack TJ. extending a connection from the toll or local and also opens thecircuit of the dialingpilot; signal DPjto efface the same. In case the AL may also be used by the operator to converse with either the calling or called subscriber in a connection between a toll or local substation and a substation terminating at an automatic main exchange such as just described as is readily apparent from the 'de tailed description of this operation relative,

to the connection between'the tollor local substations A and BL 1 In describing the operation of my inven- I tion I have described the connections between two'tollor local substations and a toll or local substation and an automatic main exchange substation. In these connections I have used the plug P of the cord C as the answering plug and the plug P as the calling-plug but the cord circuit C of my invention isof the universal type in which the plugs Pand P may be used interchangeably for either answering a call from a calling toll or magneto line or for extending a connection to an automatic main exchange through the medium of thetrunkjack TJ. The dialing control: relays DC and DCare associated, respectively, with the plugs P and P and, through the medium of the dialingkeys DK and DK, the impulse or calling device D may be connected with either plug P or P depending upon which plug is connected to the trunk A polarized relay PL, associated with the plug P, operates in amannersimilar to that describedabove in connection with the relay PL should the plug P be connected with the trunk jack TJ. As it is'readily apparent, from the previous description, how the cord C will operate should they plug P be used for answering a call from the toll substa tion A andthe plug P beused for'extending a connection to a called toll substation as B or for extending a connection to a main automaticexchange throughfthe medium of the trunk jack TJ, a detailed description of such a connection is not though While I have illustrated anddescribed a specific form of my invention, it is to be understood that my invention may be modifled by those skilled in the art without departing from the spirit of my invention and I therefore do not wish to be limited to the exact circuit arrangement as shown but aim to cover all such changes and modifications as. come withinthe spirit and scope of the appended claims. I

Having described my invention what I claim is new and desire to secure by United States Letters Patent isl. A telephone system including telephone lines and cord circuits for use in interconnecting them as. calling and called lines, a trunk line having directive impulse controlled mechanism at its distant end, a pair of plug terminals for each of said cord circuits, means for interchangeably-connecting said terminals with a calling line or with said trunk terminal, an impulse device common to said cord circuits, manual means common to said cords, and means in said cords, respectively, controlled by said key for bridging said impulse device across said connected trunk.

'2. A telephone system including telephone lines and cord circuitsffor interconnecting them as calling and called lines, a trunk line having directive impulse controlled mechanism at its distant end, a pair of plug terminals for each of said cord circuits, means for interchangeably connecting said plug terminals with a calling line or with said trunk line, an impulse device common to said cord circuits, a listening key for said connected cord, manual means common tosaid cords, and means in said cord for operatively connecting said impulse device to said connected trunk controlled by said listenin key and said manual means.

3; A telephone system including telephone lines and cord circuits for interconnecting them as calling and called lines, a trunk line having directive impulse controlled mechanism at its distant end, a pair of plug terminals for each of said cords, means for interchangeably connecting the terminals of a cord with a calling line or with said trunk line, an impulse device common to said cord circuits, a listening key in said connected cord, manual means common to said cords, means in said cord controlled by said listeningkey and manual means for bridging said impulse device across said connected trunk, and locking means for holding said impulse dial bridged across said'trunk.

4. A telephone system including telephone lines and cord circuits for interconnecting them as calling and called lines, a trunk line having directive impulse controlled mechanism at its distant end, a pair of plug terminals for each of said cords, means for interchangeably connecting either terminal of a cord with a calling line or with said trunk line, an impulse device common to said cord circuits, a listening key, manual means common to said cords, means in said cord controlled by said key and said manual means for bridging said impulse device across said connectedtrunk, means for hold-- ing said impulse dial bridged across said connected trunk during the sending of impulses to operate said impulse controlled mechanism at the distant end-of said trunk.

5. A telephone system including telephone lines and cord circuits for interconnecting them as calling and called lines, a trunk line having directive impulse controlled mechanism at its distant end, a pair of plug ter minals for each of said cords, means for interchangeably connecting either terminal of a cord with a calling line or with said trunk line, an impulse device common to said cord circuits, manual means common to said cords, means in said cord controlled by said manual means for bridging said impulse device across said connected trunk, means for holding said impulse dial bridged across said trunk during the sending of impulses to operate said impulse controlled mechanism at the distant end of said trunk and means at the distant end of said trunk for releasing said holding means.

6. A telephone system including telephone lines and cord circuits for interconnecting them as calling and called lines, a trunk line having directive impulse controlled mechanism at its distant end, a pair of plug terminals for each of said cords, means for interchangeably connecting either terminal of a cord with a calling line or with said trunk terminal, an impulse device common to said cords, manual means common to. said circuits, a listening key, means in said connected cord controlled by said key and said manual means for bridging said impulse device across said trunk, said means maintaining said bridge during the sending of, a series of impulses, means in said cord for restoring said bridging means, and means at the distant end of said trunk for effecting the operation of said restoring means at the completion of the series of impulses.

7. A telephone system including magneto telephone lines and cord circuits for interconnecting them as calling and called lines, a trunk line having directive impulse controlled mechanism at its distant end, a pair of plug terminals for each of said cords, means for interchangeably connecting either terminal of a cord with a calling magneto line or with said trunk line, an impulse device common to said cords, a listening key for the connected cord, a dial connecting key common to said cords, means under the control of said listening key, and means controlled by said connecting key through said means controlled by said listening key for bridging said impulse device across said connected trunk.

8. A telephone system including magneto elephone ines and. cord. circuits for inter connecting them as calling and called lines, a trunk line having directive impulse controlled mechanism at its distant end, a pair of plug terminals for each of said cords, means for interchangeably connecting either terminal of a cord to a calling magneto line or to said trunk line, an impulse device common to said cords for transmitting impulses to said mechanism, a listening key for the connected cord, a dial connecting key, common to said cords, means in said cord under the control of said listening key, a relay initially controlled by said connecting key through said means controlled by said listening key for bridging said impulse device across said connected trunk, and a second relay in said cord, operated when said impulse device is bridged across said trunk, and a circuit for said first mentioned relay controlled by said second relay.

9. A telephone system including magneto telephone lines and cord circuits for interconnecting them as calling and called lines, a trunk line having directive impulse controlled mechanism at its distant end, a pair of plug terminals for each of said cord circuits, means for interchangeably connecting either terminal of a cord to a calling line or to said trunk line, relays, one associated with each of the plug terminals of a connected cord, an impulse device common to said cord circuits, an impulse device connecting key controlling the said relay associated with the plug terminal of the cord connected to said trunk to bridge said impulse device across said trunk.

10. A telephone system including magneto telephone lines and cord circuits for interconnecting them as calling and called lines, a trunk line having directive impulse controlled mechanism at its distant end, a pair of plug terminals for each of said cord circuits, means for interchangeably connecting either terminal of a cord ircuit to a calling line or to said trunk line, relays, one associated with each of the plug terminals of a connected cord, an impulse device common to said link circuits, a listening key for said connected cord, a dial connecting key, means ing key for said connected cord, means in said cord controlled by said listening key, manual means common to said cords initially controlling said relay circuit through said first mentioned means, a second relay in said cord energized over said trunk when said first relay operates, to hold said first relay operated to maintain said impulse device in bridge of said trunk during the transmission of impulses.

12. A telephone system including telephone lines and cord circuits for interconnecting them, a trunk line having directive impulse controlled mechanism at its distant end, plug terminals, one for each end of each of said cords, means for interchangeably connecting either terminal of a cord to a calling line or to said trunk, a relay in said cord associated with the plu said trunk, a circuit or said relay, a listening key for the connected cord, means in said cord controlled by said listening key, manual means common to said cords initially controlling said relay circuit through said first mentioned means, a second relay in said cord, energized over said trunk when said first relay is initially operated, to hold said first relay operated to maintain said impulse device in bridge of said trunk during the transmission of impulses and means in said trunk for afi'ecting said second relay at the termigaton of said impulses to interrupt said r1 ge.

Signed b me at Chicago, in the county of Cook and tate of Illinois, this 12th day of June, 1929.

BERT WALLACE.

in said cord circuit under the control of said listening key, said dial key controlling the one of said relays associated with the plug terminal of the cord joined to said trunk through said means under the control of said listening key to bridge said impulse device across said trunk.

11. A telephone system including telephone lines and cord circuits for interconnecting them, a trunk line having directive impulse controlled mechanism at its distant end, a pair of plug terminals for each of said cords, means for interchangeably connecting either terminal of a cord with a calling line or with said trunk, a relay in said cord associated with the plug terminal connected to said trunk, a circuit for said relay, a listenterminal connected to V 

